JP4917028B2 - Intracavity medical device having an asymmetric member - Google Patents

Description

Disclosure details

[Cross-reference of related applications]
The present invention relates to 35U. S. C. Claim Priority of US Provisional Application No. 60 / 584,375 filed 30 June 2004 in accordance with §119 (e).

(Field of the Invention)
The present invention relates generally to an expandable intraluminal medical device for use in a body passage or duct, and more particularly to an optimized stent having asymmetric strut and loop members.

BACKGROUND OF THE INVENTION
The use of an endoluminal prosthesis device has proven to be an alternative to conventional vascular surgery. Intraluminal prosthetic devices are commonly used as vascular liners to repair aneurysms, or are used to mechanically support and prevent collapse of stenotic or occluded vessels.

  Intraluminal endovascular prosthesis requires the insertion of a generally tubular prosthetic device, such as a stent, percutaneously into a vessel or other tubular structure within the vasculature. Stents are typically delivered in a low-profile (pre-deployment) state using a catheter to a predetermined location within the vascular system. Once delivered to the desired location, the stent is deployed by expanding into the vessel wall. Expanded stents typically have a diameter that is several times larger than the diameter of the stent in the compressed state. Stent expansion can be accomplished by several methods known in the art, such as mechanical expansion devices (balloon catheter expansion stents) or by self-expansion.

  An ideal stent utilizes the smallest width and wall thickness of the stent member to minimize post-implantation thrombosis at the stent site. An ideal stent also has sufficient hoop strength to prevent elastic recoil of the vessel. In order to meet these requirements, many current tubular stents have a circumferential set of strut members connected by a straight length connector or a wavy length connector. ).

  The circumferential set of strut members is usually formed from a series of diagonal sections, which are connected to a curved or arcuate section to form a closed ring zigzag structure. Forming. This structure opens as the stent expands to form an element in the stent that structurally supports the vessel wall. A single strut member can be thought of as a diagonal section connected to a curved section in one of the circumferential sets of strut members. In current stent structures, these sets of strut members are formed from a single piece of metal and have a uniform wall thickness and a substantially uniform strut width. Similarly, the curved loop member is formed to have a substantially uniform wall thickness and a substantially uniform width.

  Although the geometry of the stent member may be uniform, the strain experienced by each loaded member is not uniform. The “stress” applied to the stent across any cross-section is defined as the force per unit area. These dimensions are pressure dimensions and are equal to the energy per unit volume. The stress on the stent includes the force that the stent experiences during deployment and includes the reaction force per unit area applied to the stent from the vessel wall. The resulting “strain” (deformation) experienced by the stent is defined as a slight extension perpendicular to the cross-section under consideration.

  During and during deployment, each stent member is subjected to various loads along its length. In particular, the radial arc member receives a larger load than other parts of the structure. If the stent members are all of a uniform cross-sectional area, the resulting stress and hence the strain will change. Thus, when a stent has a substantially uniform cross-section member, some stent members are over-designed in regions where the induced strain is less, resulting in a stiffer stent at all times. At a minimum, each stent member must be designed to prevent breakage by making the member size (width and thickness) sufficient to accommodate the maximum stress and / or strain experienced. Although stents with strut members and arc members having a uniform cross section will also function, increasing the width of the members to increase strength or radiopacity will cause the set of strut members to expand more when expanded. Subject to large stresses and / or strains. High stress and / or strain can cause the metal to crack due to the periodic stress of the beating heart and fatigue the stent.

Periodic fatigue damage is particularly important because the heart beats, and therefore because of the “pulse” of the artery, which is usually more than 70 times per minute and about 40 million times per year, These devices need to be designed to withstand more than 10 ⁸ loads over a 10 year lifetime. Currently, both physical testing and analytical evaluation of structures are performed to ensure acceptable stresses and strains when considering physiological loads. This is typically done using a conventional stress / strain life (SN) approach. This approach provides a design and life prediction from a combination of numerical stress predictions and an experimental determination of the relationship between applied stress or strain and the total life of the part. Fatigue loads for this description include, but are not limited to, stent axial loads, bending, torsion / torsion loads, individually and / or in combination. As those skilled in the art will appreciate, other fatigue loading conditions can also be considered using the fatigue techniques described as part of the present invention.

  Typically, finite element analysis (FEA) techniques have been used to calculate stent stress and / or strain when applied to vessels in the human body and to analyze fatigue safety. However, such conventional stress / strain life approaches to fatigue analysis only consider geometric changes that are essentially uniform to achieve acceptable stress and / or strain. We do not consider optimizing the shape to obtain a substantially uniform stress and / or strain along the structural member. The uniform stress means that the “fatigue safety factor” is uniform. Fatigue safety factor refers to a numerical function calculated from mean stress and alternating stress measured during a simulated fatigue cycle. Furthermore, the presence of flaws in the structure and the impact on the life of the stent due to the propagation of such flaws are usually not considered. Furthermore, no optimization of the geometric shape is performed in consideration of the wound in the stent structure and the effect of propagation of such a wound.

  What is needed is a stent structure in which the structural member experiences substantially uniform stress and / or strain along the member, thereby maximizing fatigue safety factor and / or minimizing peak strain. This is an analysis method that determines and optimizes the structure both in the presence and absence of defects. One such resulting structure allows for a stent member with a varying cross-section, which can stress and / or strain for a given load condition with or without defects or defects. Make it almost uniform.

[Summary of the Invention]
The present invention relates generally to an expandable intraluminal medical device for use in a body passage or duct, and more particularly to an optimized stent having asymmetric strut and loop members. In one embodiment of the invention, the stent has a proximal open end and a distal open end, and defines a longitudinal axis extending between the proximal open end and the distal open end. One or more hoop components having a shape are provided. Each hoop component is formed as a continuous series of radial strut members and a plurality of radial arc members connecting adjacent radial struts, oriented substantially longitudinally. At least one radial arc member has a non-uniform cross section, and when the radial arc deforms, the strain is distributed substantially uniformly along the radial arc.

  Another embodiment of the invention includes a stent having one or more flex connectors having at least one flex component. The bending component is designed to have a non-uniform cross-section, and when the bending component is deformed, the strain is distributed substantially uniformly along the bending component.

  Similarly, in another embodiment of the invention, a stent includes one or more radial support members having at least one radial component. The radial component is designed to have a non-uniform cross section, and when the radial component is deformed, the strain is distributed substantially uniformly along the radial component.

  In yet another embodiment of the present invention, the stent comprises one or more members, each member having at least one component. The component is designed to have a non-uniform cross section, and when the component is deformed, the strain is distributed substantially uniformly along the component.

  In yet another embodiment of the invention, the stent has a proximal open end and a distal open end and defines a longitudinal axis extending between the proximal open end and the distal open end. A plurality of hoop components having a tubular shape. Each hoop component is formed as a continuous series of radial strut members and a plurality of radial arc members connecting adjacent radial struts, oriented substantially longitudinally. At least one radial arc member has a non-uniform cross section, and when the radial arc deforms, the strain is distributed substantially uniformly along the radial arc. The stent further comprises one or more flex connectors oriented longitudinally that connect adjacent hoop components. Each flex connector includes a flexible strut, and each flexible strut is connected at each end by a single flexible arc.

  Another stent according to the present invention has a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end. Having one or more hoop components. Each hoop component is formed as a series of radial strut members that are substantially longitudinally oriented and a radial arc member that connects adjacent radial struts. The at least one radial arc member has a non-uniform cross section, and when the radial arc is deformed, the stress is distributed substantially uniformly along the radial arc.

  Yet another medical device according to the present invention comprises a stent including one or more flex connectors having at least one flex component. The bending component has a non-uniform cross section and when the bending component is deformed, the stress is distributed substantially uniformly along the bending component.

  The present invention also contemplates one or more radial support members that include at least one radial component. The radial component has a non-uniform cross-section, and when the radial component is deformed, the stress is distributed substantially uniformly along the radial component.

  Another stent according to the present invention comprises one or more members each having at least one component. The component has a non-uniform cross section, and when the component is deformed, the stress is distributed substantially uniformly along the component.

  Yet another stent according to the present invention has a tubular shape having a proximal open end and a distal open end and defines a longitudinal axis extending between the proximal open end and the distal open end. A plurality of hoop components. Each hoop component is formed as a continuous set of radial strut members disposed substantially in the lengthwise direction and a plurality of radial arc members connecting adjacent radial struts. At least one radial arc member has a non-uniform cross section, and when the radial arc deforms, the stress is distributed substantially uniformly along the radial arc. The stent further comprises one or more flex connectors disposed longitudinally that connect adjacent hoop components. Each flex connector includes a flexible strut, and each flexible strut is connected at each end by a single flexible arc.

  Yet another stent according to the present invention has a tubular shape having a proximal open end and a distal open end, and defines a longitudinal axis extending between the proximal open end and the distal open end. One or more hoop components are provided. Each hoop component is formed as a continuous set of radial strut members disposed substantially in the lengthwise direction and a plurality of radial arc members connecting adjacent radial struts. At least one radial arc member has a non-uniform outer shape, and when the radial arc deforms, the stress is distributed substantially uniformly along the radial arc.

  The present invention also contemplates a stent having one or more flexible connectors that connect adjacent hoop components. Each flexible connector is formed as a continuous set of flexible strut members disposed substantially in the lengthwise direction and a plurality of flexible arc members connecting adjacent flexible struts. Yes. The at least one flexible arc member has a tapered profile, and when the flexible arc is deformed, the strain is distributed substantially uniformly along the flexible arc.

Detailed Description of the Invention
The present invention describes an intraluminal medical device that can be expanded into the wall of a vessel lumen and is subject to physiological loads. While maintaining a substantially uniform stress (uniform fatigue safety factor) and / or strain in one or more of the components of the device during use. For purposes of this description, “use” may include delivery, deployment, and post-deployment (short term or long term) status of the device. An intravascular stent is described for illustrative purposes. However, as the term is used herein, intraluminal medical devices include, but are not limited to, any expandable intravascular prothesis, expandable endovascular prothesis, Includes stents or any other mechanical scaffolding device used to maintain or expand body passageways. In addition, in this regard, the term “body passageway” encompasses any duct or any body vessel in the body of a mammal and is limited to any body vessel. Although not, any vein, artery, duct, vessel, passage, trachea, urethra, esophagus, and any artificial vessel such as a graft are included.

  Intraluminal devices according to the present invention may include any radially expandable stent, including self-expanding stents and mechanically expandable stents. Mechanically expanded stents include, but are not limited to, stents that are radially expanded by an expansion member, such as by balloon inflation.

  With respect to the drawings, like parts are designated by like reference numerals throughout the various different figures. For example, the radial strut 108 in FIG. 1 is similar to or equivalent to the radial strut 308 in FIG.

  With reference to FIGS. 1 and 2, a perspective view of a stent 100 according to one embodiment of the present invention is illustrated. FIG. 1 illustrates the stent 100 in an unexpanded or constrained pre-deployment state, while FIG. 2 illustrates the stent 100 in a fully expanded state.

  The stent 100 comprises a structural member having a tubular shape, the structural member having a tubular shape having a proximal open end 102 and a distal open end 104 between the proximal open end 102 and the distal open end 104. Defines a longitudinal axis 103 extending in the direction of. The stent 100 has a first diameter D1 suitable for insertion into a patient and progressing through a vessel, and a second diameter D2 suitable for placement in a target region of a blood vessel, the second diameter. Is larger than the first diameter.

  The stent 100 structure comprises a plurality of adjacent hoops 106 (a) -hoops 106 (d) that are connected to the proximal end 102 and the far end 106 (d). Extending between the distal ends 104. In the illustrated embodiment, the hoop 106 (a) -hoop 106 (d) includes various radial support members and / or components. Specifically, the radial components constituting the hoops 106 (a) to 106 (d) include a plurality of radial strut members 108 arranged in the length direction and a plurality of radials connecting adjacent radial struts 108. There are radial arc members 110. Adjacent radial struts 108 are connected so as to form a substantially S-shaped or Z-shaped pattern at opposite ends so as to form a plurality of cells. The plurality of radial arc members 110 have a substantially semicircular shape and are substantially symmetric with respect to the center thereof.

  The stent 100 structure further includes a plurality of bent connectors 114, which connect the adjacent hoops 106 (a) to 106 (d). Each flex connector 114 includes one or more flexible components. In the embodiment illustrated in FIGS. 1 and 2, the flexible component includes one or more longitudinally oriented flexible strut members 116 and a plurality of flexible arc members 118. Adjacent flexible struts 116 are connected in a substantially N-shaped pattern at opposite ends. The plurality of flexible arc members 118 have a substantially semi-circular shape and are substantially symmetric with respect to the center thereof.

  Each flex connector 114 has two ends. One end of the flex connector 114 is attached to one radial arc 110 of one hoop, eg, the hoop 106 (c), and the other end of the flex connector 114 is attached to an adjacent hoop, eg, , Attached to one radial arc 110 of the hoop 106 (d). The bent connector 114 connects the adjacent hoops 106 (a) to 106 (d) together with a bent connector to a radial arc connection region 117.

  FIG. 3A illustrates a stent 300 according to one embodiment of the present invention. The stent 300 appears to have been cut lengthwise and laid flat in a two-dimensional shape, but is in a state prior to being restrained and deployed. As can be clearly seen, the stent 300 depicted in FIG. 3A is actually cylindrical, similar to the stent 100 shown in FIG. It is only shown. Such a cylindrical shape can be obtained by winding the flat shape of FIG. 3A into a cylindrical shape and joining the top point “C” to the bottom point “D”.

  The stent 300 is usually manufactured by laser machining a cylindrical cobalt-chromium alloy tube. Other materials that can be used to manufacture the stent 300 include other non-ferrous metal alloys such as cobalt and nickel based alloys, nickel titanium alloys, stainless steel, other ferrous metal alloys, refractory metals, Includes refractory metal alloys, titanium and titanium based alloys. Stents may also be made from ceramic or polymeric materials.

  Similar to FIG. 1, the stent 300 is comprised of a plurality of cylindrical hoops 306 that are attached together by a plurality of flex connectors 314. By way of example, radial strut members 308b are connected between radial arc members 310b to form a closed cylindrical hoop section 306b (as shown in dotted rectangle 312) in FIG. 3A. .

  A section of flex connectors 314 bridges adjacent hoop sections 306 (as shown in dotted rectangle 326). Each set of flex connectors 314 consists of three flexible struts 316 oriented in the lengthwise direction, each flexible strut 316 being connected by one of four flexible arc members 318 at each end. Thus, it can be said that an “N-shaped” flexible connector 314 having two ends is formed. Each end of the N-shaped bent connector 314 is attached to the curved radial arc member 310 at a strut bent connector attachment point 317.

  In the illustrated embodiment, each hoop section 306 is comprised of a radial strut 308 and a radial arc 310 arranged in a generally sinusoidal pattern. Each flex connector is attached to an adjacent hoop 306 for every complete sinusoidal cycle so that the number of N flex connectors 314 in the set of N flex connectors 326 is equal to the number in the hoop section 306. This is half the total number of radial arc members 310. FIG. 3E depicts details of a typical flex connector 314, which has a flexible strut 316 oriented longitudinally, the flexible strut 316 at each end. To the flexible arc 318.

  Each N-shaped bent connector 314 is formed to nest with an adjacent N-shaped bent connector 314 as clearly shown in FIG. 3A. “Nesting” means that the top of the first flexible connector is the bottom of the second flexible connector that is installed directly above the first flexible connector. It is defined as inserting beyond. Similarly, the bottom of the first flexible connector is inserted just below the top of the third flexible connector that is installed directly below the first flexible connector. Thus, in a stent in which individual flexible connectors are nested, each flexible connector has an adjacent flexible connector, that is, a flexible connector immediately below the individual flexible connector, and Nested with the flexible connector just above. By nesting in this manner, the stent 300 can be constrained to a smaller diameter without overlapping “N-shaped” bent connectors 314.

  The stent 300 illustrated in FIG. 3A is comprised of nine hoop sections 306 that are connected by eight sections of a flexible connector 314. The nine hoop sections 306 include two end hoop sections (proximal hoop section 306a and distal hoop section 306c) and seven internal hoop sections 306b.

  The inner hoop section 306b is connected in a predetermined pattern at both ends by the section of the flex connector 314 to form a plurality of closed cells 320. The end hoop sections (306a and 306c) are connected at one end to adjacent internal hoop sections by a section of flex connector 314, which also forms a plurality of closed cells. Adjacent hoop sections 306 may be oriented out of phase as illustrated in FIG. 3A. Alternatively, adjacent hoop sections 306 may be oriented so that they are in phase. The length of the end hoop sections (306a and 306c) in the length direction may be different from the length of the inner hoop section 306b in the length direction. In the embodiment illustrated in FIG. 3A, the end hoop sections (306a and 306c) have a shorter length than the inner hoop section 306b.

  As previously described, each hoop section in the illustrated embodiment is comprised of a radial strut member 308 and a radial arc member 310 arranged in a generally sinusoidal pattern. Each repeating wavy pattern forms a hoop element 322. The hoop elements repeat at each flex connector 314 (in a given set of flex connectors 326) to form a hoop 306.

  For example, FIG. 3A shows that each hoop section 306 is comprised of five hoop elements 322. However, the number of repeating hoop elements 322 is not meant to limit the scope of the present invention. As will be appreciated by those skilled in the art, a greater or lesser number of hoop elements may be used, particularly when providing larger or smaller diameter stents. A hoop element may be used.

  3B-3D are enlarged detailed views of a proximal hoop element 322a, an inner hoop element 322b, and a distal hoop element 322c, respectively, according to an embodiment of the present invention. Proximal end hoop element 322a is attached to flex connector 314 along the distal end of proximal end hoop element 322a. Distal end hoop element 322c is attached to flex connector 314 along the proximal end of distal end hoop element 322c. FIG. 3C illustrates a typical internal hoop element 322b that is attached to an adjacent flex connector 314 along the proximal and distal ends of the internal hoop element 322b. Yes.

  As previously described, the hoop element 322 includes a plurality of radial struts 308 and radial arcs 310 arranged in a generally sinusoidal pattern. In order to make the stress or strain uniform in each element of the wavy pattern, the hoop elements 322 are generally comprised of radial struts 308 and radial arcs 310 that vary in dimensions within each hoop element 322. Such design shapes include radial struts 308 having different cross-sectional areas. Further, the proximal end hoop element 322a and the distal end hoop element 322c have a different shape than the inner hoop element 322b. Thus, the radial arc 310 and radial strut 308 members that are part of the inner hoop element 322b may be sized differently from the corresponding struts of the proximal end hoop element 322a and the distal end hoop element 322c, respectively. Proximal hoop element 322a and distal hoop element 322c are mirror images of each other.

  Intravascular stents must be stiff in the circumferential direction and have sufficient hoop strength to prevent vascular recoil while maintaining longitudinal flexibility. In typical sinusoidal and nearly sinusoidal designs, the radial arc has areas of high stress or strain, which are directly related to stent fatigue. However, the stresses and / or strains that occur along the length of the radial arc are not uniform and there are regions where the stresses and / or strains are relatively low. If the stent has a radial arc with a uniform cross-section, regions with high maximum stress and / or strain and other regions with relatively low stress and / or strain will result. The result of such a design is a reduction in fatigue performance as well as a reduction in expansion performance.

  The stent design according to the present invention is optimized with respect to stress (fatigue safety factor) and / or strain, so that the stent has a substantially uniform strain along a critical area of the stent, It has come to have optimum fatigue performance. Fatigue properties were optimized by maximizing a fatigue safety factor that was nearly uniform along the stent. Various important areas may include radial arc 310 and / or radial strut 308 and / or bending arc 318 and / or bending strut 316. In the preferred embodiment, the critical area includes the radial arc 310. One method of predicting stress and / or strain in a structure is finite element analysis (FEA), which utilizes finite elements (discrete locations).

  This design provides a stent with higher expandability and longer fatigue life. At the initial stress and / or high, the material is added locally to increase the cross-sectional area of the radial arc 310, thereby distributing the high local stress and / or strain to adjacent regions, and the maximum stress and / or Lowered the distortion. Furthermore, changing the cross-sectional geometry can also reduce the maximum stress and / or strain as well. Such techniques can be applied individually or in combination (ie, adding or removing cross-sectional areas and / or changing cross-sectional geometry) to stent components, eg, radial arc 310, as a result. Applied until the resulting stress and / or strain is approximately uniform. Another benefit of this design is that the stent size is reduced.

  In order to quantitatively assess pre-existing discontinuities, including defects in the stent structure, and thereby predict the fatigue life of the stent, the scope of the present invention includes numerical analysis based on fracture mechanics . Furthermore, this approach can be extended to optimizing the stent design to maximize fatigue life in the presence of discontinuities. This fracture mechanics-based approach according to the present invention involves microstructural defects with respect to the tendency of discontinuities to propagate and the stent to break in vivo when subjected to periodic loading within the implanted vessel. Quantitatively assess the severity of discontinuities in the stent structure. Specifically, stress intensity factors for different lengths, different geometries, and / or structural discontinuities with respect to different locations within and on the stent structure are described and are periodic Differences in stress intensity associated with different loads are compared to determine the threshold for fatigue crack growth and the severity of discontinuities. Experimental data on the rate of fatigue crack growth for the stent material is then used to predict the life of the stent based on the load cycle required to propagate the discontinuity to a critical magnitude.

  FIG. 4A is a graph showing the length of the discontinuity taken on the X-axis with respect to the range of stress intensity taken on the Y-axis (difference in stress intensity factor in the whole area of the fatigue load). Solid line 480 represents the threshold stress intensity range depicted as a function of discontinuity length. This threshold stress range is described for a given stent material. For a given stent design, different lengths, geometries, and / or discontinuities at different locations within and on the stent structure can cause these discontinuities to enter the stent structure. And / or numerical analysis by introduction onto the stent structure and the stress intensity range was calculated for the fatigue load in question. For example, points 481-485 dotted in FIG. 4A represent the stress intensity ranges calculated for various discontinuity lengths. When these points 481-485 fall below the threshold stress intensity curve 480 for a given length of discontinuity, the discontinuity may be present during long-term conditions after placement, particularly during use of the stent. In the meantime, the possibility of propagation is considered low. Conversely, if points 481-485 are on or above curve 480, the discontinuity is more likely to propagate during use.

  A more conservative approach can be taken by numerically integrating the fatigue crack propagation relationship between a range of initial and final discontinuity magnitudes for a given stent material. This approach ignores the existence of a threshold stress intensity range and is therefore considered more conservative. As a result of numerical integration, the lifetime for the stent is predicted as a function of the magnitude of the discontinuity. FIG. 4B is a graphical representation of the fatigue life of a stent (taken on the Y axis) as a function of the magnitude of the discontinuity (taken on the X axis) and is described by curve 490.

  Curve 490 is compared to curve 491, which is the design life of the stent, for further evaluation of stent safety. If the predicted fatigue life 490 for a given discontinuity magnitude is longer than the design life 491, a stent having such a discontinuity is considered safe. Conversely, if the predicted fatigue life 490 for a given discontinuity magnitude is greater than or equal to the design life 491, a stent having such a discontinuity is considered more susceptible to failure during use.

  5A-5C can be used to compare the strain experienced by a stent according to one embodiment of the present invention with a typical prior art stent shape. FIG. 5A shows an enlarged detail view of a radial arc 510a for a prior art stent and an adjacent radial strut 508a (hereinafter referred to as stent section 530a). As shown in the illustrated section 530a, the radial arc 510a has a uniform width throughout its length.

  FIG. 5B is a similar enlarged detail view of a radial arc 510b for a stent and an adjacent radial strut 508b (hereinafter stent section 430b) according to one embodiment of the present invention. Unlike the prior art stent section 530 shown in FIG. 5A, the radial arc 510b is non-uniform in width to achieve a substantially uniform strain throughout the radial arc 510b.

  In this description, distortion optimization is described as an example. However, as will be appreciated by those skilled in the art, the method could also be applied to optimize stress conditions as well.

  For comparison, the strain at five position points (1-5) along each illustrated stent section 530 was measured for a given expanded diameter. Position point 1 is disposed along radial strut 508. Position point 2 and position point 4 are located at each proximal end of radial arc 510 where radial arc 410 is connected to radial strut 508. The position point 3 is arranged along the top of the radial arc 510, that is, along a predetermined position near or at the radial midpoint.

  A graph comparing the strain experienced by the prior art stent section 530a with the strain experienced by the stent section 530b for a given expanded diameter is shown in FIG. 5C. The strain experienced by the prior art stent is indicated in the graph by curve C1, having a non-uniform strain, and the strain position points are indicated by diamonds. The total strain experienced by the prior art stent section 530a is the area under curve C1.

  The strain experienced by a stent according to an embodiment of the present invention is indicated in the graph by curve C2, with improved strain, and the strain position points are shown as squares. The total strain experienced by the prior art stent section 530b is the area under curve C2. Since both sections 530a and 530b are expanded in the same way, the total distortion is equal. That is, the area below the curve C1 is equal to the area below the curve C2.

  The strains and loads shown are examples and do not depict actual conditions or results. Rather, the strain shown is used for comparison purposes to account for the effect of loading on stent components having different geometries.

  Referring to FIG. 5C, the strain experienced by the prior art stent is relatively small at position points 1 and 2, reaching about 8 strains at the base of radial arc 510a (position point 2). The strain then increases significantly to a maximum strain of about 50% at position point 3, the top of the radial arc 510a. The strain received is substantially symmetric with respect to the top of the radial arc 510, with a significant reduction to about 8 strain at the base of the radial arc 510a (position point 4) and almost 0% for the radial strut 508 at position point 5. It becomes.

  In contrast, the strain for stent section 530b is relatively small at position point 1, but increases more uniformly between position point 2 and position point 3, and the base of radial arc 510b (position point 2 ) Reaches about 18%, and the top of radial arc 510b (position point 3) reaches 35%. Similar to curve C1, curve C2 is substantially symmetric about position point 3.

  As can be seen in FIGS. 5A-5C, changing the material cross-section (adding or removing material) at the radial arc base (position point 2 and position point 4) increases the strain caused. This reduces the distortion caused at the top of the radial arc (position point 3). This is because the total distortion experienced by this section does not change. Furthermore, changing the cross-sectional area (adding or removing material) along the top of the radial arc 510b (position point 3) reduces the strain caused. This automatically increases the distortion caused at the base of radial arc 510b (position points 2 and 4). Such changes can be made individually, as described above, or combined and repeated to develop an improved stent section 530b with a substantially uniform strain along the radial arc 530b. Can also be done.

  One advantage of having a nearly uniform distortion is that the peak distortion (shown at position point 3) is greatly reduced. As a result, the stent can be expanded to a larger expansion diameter, and the induced strain is still in a safe operating range. For example, the stent represented by curve C2 could be increased in diameter until the peak strain at position point 3 increases from 35% to 50%.

  The stent 300 according to an embodiment of the present invention is cut with a laser from a thin metal tube having a substantially uniform wall thickness. In order to change the cross-section of the stent components, particularly the radial arc 310, the components are tapered to increase the width of the heavily loaded region so that the stress and / or strain is substantially uniform. Of course, the taper need not be uniform, that is, the radius need not always change. Rather, the width of radial arc 310 depends on the resultant stress and / or strain that radial arc 310 experiences at various locations along its length.

  3B-3D illustrate a hoop element 322 with a tapered radial arc 310 according to one embodiment of the present invention.

  Referring to FIG. 3B, a proximal hoop element 322a is shown in accordance with one embodiment of the present invention. The hoop element 322a is composed of two radial struts 308a1 and 308a2 and two different radial arcs 310a1 and 310a2. Although radial struts 308a1 and radial struts 308a2 are shown as having different profiles in the illustrated embodiment, this should not be construed as limiting the scope of the invention. In other embodiments, the radial struts may have the same or substantially the same outer shape.

  The radial arc 310a1 connects the radial strut 308a2 to the radial strut 308a1, and is not connected to the bending connector 314. Since the radial arc 310a1 is not connected to the flex connector 314, the radial arc 310a1 receives a substantially balanced load and thus has a substantially symmetric geometry (radial struts (308a1 or 308a2). ) Connection points 315a have substantially equal cross-sections), maintaining substantially uniform stress and / or strain throughout. The substantially midpoint of the radial arc 310a1 according to the illustrated embodiment receives a slightly larger load than the connection point 315a of the radial arc 310a1. To accommodate larger loads and maintain a substantially uniform stress and / or strain throughout the radial arc 310a1, the midpoint of the radial arc 310a1 is thicker than the connection point 315a for the radial arc radial strut (more Have a wide width).

  Conversely, the radial arc 310a2 is directly connected to the bent connector 314 and receives a load that is not balanced. In order to maintain substantially uniform stress and / or strain through the radial arc 310a2, the arc 310a2 has a substantially asymmetric geometry and each connection point of the radial struts (308a1, 308a2). (313a, 317a) have substantially unequal cross sections. Since the connection point 317a to the bending connector 314 of the radial arc 310a2 has a large cross section, the connection point 319a located in the immediate vicinity of the connection point 317a is slightly in order to maintain a substantially uniform stress and / or strain. It may have a small width. The approximate midpoint of the radial arc 310a2 according to the illustrated embodiment is subjected to a slightly greater load than the connection points 313a and 319a of the radial arc 310a2. To accommodate larger loads and maintain substantially uniform stress and / or strain throughout the radial arc 310a2, the midpoint of the radial arc 310a2 is greater than the connection points 313a and 319a for the radial arc radial struts. Also thicker (has a wider width).

  FIG. 3C shows an internal hoop element 322b according to one embodiment according to the present invention. The hoop element 322b includes a radial strut 308b1 and a radial strut 308b2, and a radial arc 310b1 and a radial arc 310b2. Each radial arc (310b1, 310b2) connects the radial strut 308b1 to the radial strut 308b2. Each radial arc (310b1, 310b2) is also connected to the flex connector 314 near the connection point with the radial strut 308b2. Since the radial hoop element 322b is substantially symmetric, the radial arcs (310b1, 310b2) are subjected to a substantially balanced load and, for this reason, connection points 315b having a substantially symmetric geometry. 313b and 319b (having substantially equal cross-sections), maintaining substantially uniform stress and / or strain. The substantially midpoint between the radial arc 310b1 and the radial arc 310b2 according to the illustrated embodiment is subjected to a slightly larger load than the connection point 315b, the connection point 313b, and the connection point 319b of the radial arc 310b1 and the radial arc 310b2. In order to accommodate larger loads and maintain substantially uniform stress and / or strain throughout the radial arc 310b1, 310b2, the midpoint of the radial arc 310b1, radial arc 310b2 is the connection point of the radial arc to the radial strut. It is thicker (has a wider width) than 315b, connection point 313b and connection point 319b.

  FIG. 3D illustrates a distal hoop element 322c according to one embodiment of the present invention. As described above, the distal hoop element 322c is a mirror image of the proximal hoop element 322b shown in FIG. 3B. Thus, the load and the resulting strut member geometry are similar.

  A distal hoop element 322c according to an embodiment of the invention is shown. The hoop element 322c is composed of two radial struts 308c1 and 308c and two different radial arcs 310c1 and 310c2.

  The radial arc 310c1 connects the radial strut 308c2 to the radial strut 308c1, and is not connected to the bending connector 314. Since the radial arc 310c1 is not connected to the flex connector 314, the radial arc 310c1 is subjected to a substantially balanced load and thus has a substantially symmetric geometric shape (radial strut (308c1 or 308c2 ) Have substantially equal cross-sections) and maintain substantially uniform stress and / or strain throughout. The substantially midpoint of the radial arc 310c1 according to the illustrated embodiment receives a slightly larger load than the connection point 315c of the radial arc 310c1. In order to accommodate larger loads and maintain a substantially uniform stress and / or strain throughout the radial arc 310c1, the midpoint of the radial arc 310c1 is thicker than the connection point 315a to the radial arc radial strut (more Have a wide width).

  Conversely, the radial arc 310c2 is directly connected to the flex connector 314 and receives an unbalanced load. In order to maintain substantially uniform stress and / or strain throughout the radial arc 310c2, the arc 310c2 has a substantially asymmetric geometry and each connection point (308c1, 308c2) of the radial strut (308c1, 308c2). 313c, 317c) have substantially unequal cross sections. Since the connection point 317c to the bending connector 314 of the radial arc 310c2 has a large cross section, the connection point 319c located in the immediate vicinity of the connection point 317c is slightly narrow to maintain a substantially uniform stress and / or strain. It may have a width. The substantially midpoint of the radial arc 310c2 according to the illustrated embodiment is subjected to a slightly greater load than the connection points 313c and 319c of the radial arc 310c2. In order to accommodate larger loads and maintain a substantially uniform stress and / or strain throughout the radial arc 310c2, the midpoint of the radial arc 310c2 is greater than the connection point 313c and connection point 319c for the radial arc radial strut. Also thicker (has a wider width).

  The stent design according to the present invention was optimized to minimize maximum stress and / or strain to obtain a stent having stress and / or strain that is substantially uniform at each point along the flex connector 314. May be. Such a design provides a more flexible stent with an initially measured load, and a bent connector section with a smaller cross section, with lower stress and / or strain. The criteria described above (ie, adding or removing a cross-section) are applied to the flex connector 314 until the resulting stress and / or strain is substantially uniform.

  Since radial struts 308 experience relatively low stresses and / or strains compared to flex connectors 314 and radial arcs 310, tapering struts 308 minimizes maximum stresses and / or strains against fatigue resistance. It is usually not necessary to do that. However, as shown in FIGS. 3A-3D, increasing the cross-section of the radial strut 308 makes it difficult for radiation to pass through the strut 308 and therefore the stent 300. This improves the visibility of the stent during the X-ray examination procedure. Increasing the cross section of the strut 308 includes shaping, that is, adding a shape to the strut to increase the size of the strut. In some embodiments, a bulge shape 309 is added to the strut 308 of the stent. However, as will be appreciated by those skilled in the art, the type of geometry applied to strut 308 is not intended to limit the scope of the present invention.

  In addition to the embodiments described above, therapeutic or pharmaceutical agents may be added to any component of the device during manufacture in order to treat many diseases. With a radial strut 308 of increased width and added shape, i.e., the outer shape gradually increases, the stent can hold more drug.

The therapeutic or pharmaceutical agent may be added to the device in the form of a drug or drug eluting layer, or by treating the surface after the device is formed. In preferred embodiments, the therapeutic and pharmaceutical agents may include any one or more of the following: vinca alkaloids (ie, vinblastine, vincristine, and vinorelbine) )), Paclitaxel, epidipodophyllotoxins (ie, etoposide, teniposide), antibiotics (dactinomycin (actinomycin D)) Daunorubicin, doxorubicin, and idarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin), And natural products such as mitomycin, enzymes (L Asparagine (L-asparagine) metabolize systematically and take the cell without the ability to synthesize their own asparagine L- asparaginase (L-asparaginase)); G (GP) II b / III a inhibitors and vitronectin (vitronectin) Antiplatelet agents such as receptor antagonists; nitrogen mustards (mechlorethamine, cyclophosphamide and analogs, melphalan, chlorambucil) ), Ethylenimines and methylmelamines (hexamethylmelamine and thiotepa), alkyl sulfonates-busulfan, nirtosoureas (carmustine) (BCNU) and analogs, streptozocin), tiger Antiproliferative / antimitotic alkylating agents, such as trazenes-dacarbazinine (DTIC); folic acid analogs (methotrexate, pyrimidine analogues) Pyrimidine analogs (fluorouracil, floxuridine, and cytarabine), purine analogs and related inhibitors (mercaptopurine, thioguanine, Antiproliferative / antimitotic antimetabolites such as pentostatin and 2-chlorodeoxyadenosine {cladribine}; platinum isotopes coordination complexes) (cisplatin, carboplatin), proca Procarbazine, hydroxyurea, mitotane, aminoglutethimide; hormones (ie, estrogen); anticoagulants (heparin, synthetic heparin salts) (synthetic heparin salts and other thrombin inhibitors); fibrinolytic agents (tissue plasminogen activator, streptokinase and urokinase, aspirin, dipyridamole, Ticlopidine, clopidogrel, abciximab; antimigratory: antisecretory (breveldin); anti-inflammatory: eg corticosteroids ( adrenocortical steroids (cortisol, cortisone), Ludrocortisone, prednisone, prednisolone, 6α-methylprednisolone, 6 am-methylprednisolone, triamcinolone, betamethasone, and dexamethasone, steroid Derivatives, ie aspirin; para-aminophenol derivatives, ie acetominophen; indole and indene acetic acids (indomethacin, sulindac) (sulindac) and etodalac, heteroaryl acetic acids (tolmetin, diclofenac, and ketorolac), arylpropionic acids (ibuprofen) And derivatives , Anthranilic acids (mefenamic acid and meclofenamic acid), enolic acids (piroxicam, tenoxicam, phenylbutazone, and oxyphene) Satrazone (oxyphenthatrazone), nabumetone, gold compounds (auranofin, aurothioglucose, gold sodium thiomalate), etc .; immunosuppressives ): (Cyclosporine, tacrolimus (FK-506), sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenic agents ): Vascular endothelial growth factor (VEGF), line Fibroblast growth factor (FGF); angiotensin receptor blockers; nitric oxide donors; anti-sense oligonucleotides and combinations thereof; Cell cycle inhibitors, mTOR inhibitors and growth factor receptor signal transduction kinase inhibitors; retinoids; cyclin / CDK inhibitors; HMG co-enzyme reductase inhibitors (statins); and protease inhibitors.

  While numerous variations of the invention have been described in detail, other modifications and uses that are expected to be within the scope of the invention will be readily apparent to those skilled in the art based on the present disclosure. Various combinations and sub-combinations of particular embodiments can be made and still be considered to be within the scope of the invention. For example, embodiments variously shown as heart stents may be modified to treat other blood vessels and lumens in the body, particularly those in which the blood vessels or lumens need to be supported. Modifications may be made to treat other areas. Thus, it should be understood that various applications, modifications, and substitutions of equivalents can be made without departing from the spirit of the invention or the scope of the following claims.

  The following claims are provided herein to illustrate examples of some beneficial aspects of the subject matter disclosed herein and within the scope of the present invention.

Embodiment
(1) In the stent,
One or more hoops having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end A series of radial strut members, each of the hoop components being substantially longitudinally oriented, and a plurality of radial arc members connecting adjacent radial struts; Formed, hoop components,
With
At least one of the radial arc members has a non-uniform cross section, and when the radial arc is deformed, strain is distributed substantially uniformly along the radial arc;
Stent.
(2) In the stent according to embodiment 1,
A stent, wherein the cross-sections have substantially equal cross-sectional areas.

(3) In the stent according to embodiment 1,
A stent, wherein the cross-sections have substantially unequal cross-sectional areas.
(4) In the stent,
One or more flex connectors having at least one flex component;
With
The at least one bending component has a non-uniform cross section, and when the bending component is deformed, strain is distributed substantially uniformly along the bending component;
Stent.
(5) In the stent according to embodiment 4,
A stent wherein the bending component is a flexible arc member.
(6) In the stent according to embodiment 5,
A stent wherein the cross-sections of the flexible arc members have substantially equal cross-sectional areas.

(7) In the stent according to embodiment 5,
A stent wherein the cross sections of the flexible arc members have unequal cross-sectional areas.
(8) In the stent according to embodiment 4,
A stent wherein the bending component is a flexible strut member.
(9) In the stent according to embodiment 8,
A stent wherein the cross-sections of the flexible strut members have substantially equal cross-sectional areas.
(10) In the stent according to embodiment 8,
A stent wherein the cross-sections of the flexible strut members have unequal cross-sectional areas.
(11) In the stent,
One or more radial support members having at least one radial component;
With
The at least one radial component has a non-uniform cross-section, and when the radial component deforms, strain is distributed substantially uniformly along the radial component;
Stent.

(12) In the stent according to embodiment 11,
A stent wherein the at least one radial component is a radial arc member.
(13) In the stent according to embodiment 12,
A stent, wherein the cross-sections have substantially equal cross-sectional areas.
(14) In the stent according to embodiment 12,
A stent wherein the cross-sections have unequal cross-sectional areas.
(15) In the stent according to embodiment 11,
A stent wherein the at least one radial component is a radial strut member.
(16) In the stent according to embodiment 15,
A stent, wherein the cross-sections have substantially equal cross-sectional areas.

(17) In the stent according to embodiment 15,
A stent wherein the cross-sections have unequal cross-sectional areas.
(18) In the stent,
One or more members, each member having at least one component,
With
The at least one component has a non-uniform cross-section and when the component deforms, the strain is distributed substantially uniformly along the component;
Stent.
(19) In the stent according to embodiment 18,
A stent wherein the cross-sections of the components have equal cross-sectional areas.
(20) In the stent according to embodiment 18,
A stent wherein the cross-sections of the components have unequal cross-sectional areas.

(21) In a stent,
A plurality of hoop components having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end Each hoop component is formed as a continuous series of radial strut members, and a plurality of radial arc members connecting adjacent radial struts, oriented substantially longitudinally. A hoop component, wherein at least one of the radial arc members has a non-uniform cross-section, and when the radial arc deforms, strain is distributed substantially uniformly along the radial arc;
One or more flex connectors oriented in a longitudinal direction connecting adjacent hoop components, each flex connector comprising a flexible strut, each flexible strut being one A bent connector connected at each end by a flexible arc;
A stent.

(22) In the stent according to embodiment 21,
A stent wherein the radial struts in at least one of the hoop sections are of equal length.
(23) In the stent according to embodiment 21,
A stent in which the flexible struts and the flexible arc that make up the flex connector are arranged in a substantially "N" shape.
(24) In a stent,
One or more hoops having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end A series of radial strut members, each of the hoop components being substantially longitudinally oriented, and a plurality of radial arc members connecting adjacent radial struts; Formed, hoop components,
With
At least one of the radial arc members has a non-uniform cross section, and when the radial arc is deformed, stress is distributed substantially uniformly along the radial arc;
Stent.

(25) In a stent,
One or more flex connectors having at least one flex component;
With
The at least one bending component has a non-uniform cross section, and when the bending component is deformed, stress is distributed substantially uniformly along the bending component;
Stent.
(26) In a stent,
One or more radial support members having at least one radial component;
With
The at least one radial component has a non-uniform cross section, and when the radial component deforms, the stress is distributed substantially uniformly along the radial component;
Stent.
(27) In a stent,
One or more members, each member having at least one component;
With
The at least one component has a non-uniform cross-section and when the component deforms, the stress is distributed substantially uniformly along the component;
Stent.

(28) In a stent,
A plurality of hoop components having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end Each of the hoop components is formed as a series of radial strut members that are substantially longitudinally oriented and a plurality of radial arc members that connect adjacent radial struts. A hoop component, wherein at least one of the radial arc members has a non-uniform cross section, and when the radial arc is deformed, stress is distributed substantially uniformly along the radial arc; and
One or more flex connectors oriented in a longitudinal direction connecting adjacent hoop components, each flex connector comprising a flexible strut, each flexible strut being one A bent connector connected at each end by a flexible arc;
A stent.

(29) In a stent,
One or more hoops having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end Each of the hoop components is formed as a series of radial strut members that are substantially longitudinally oriented and a plurality of radial arc members that connect adjacent radial struts. The hoop components,
With
At least one of the radial arc members has a non-uniform outer shape, and when the radial arc deforms, strain is distributed substantially uniformly along the radial arc;
Stent.
(30) In the stent according to embodiment 29,
The stent, wherein the at least one radial strut member is shaped to have a larger cross section.

(31) In the stent according to embodiment 30,
A stent wherein the shaped shape is a bulge.
(32) In the stent according to embodiment 29,
Inner and outer hoop components,
Have
The inner hoop component has an axial length that is longer than the outer hoop component;
Stent.
(33) In the stent according to embodiment 29,
Inner and outer hoop components,
Have
The inner hoop component has an axial length that is shorter than the axial length of the outer hoop component;
Stent.

(34) In a stent,
One or more flexible connectors connecting adjacent hoop components, each said flexible connector being a continuous stretch of flexible strut members substantially oriented longitudinally; And a flexible connector formed as a plurality of flexible arc members connecting adjacent flexible struts,
With
At least one of the flexible arc members has a tapered profile, and when the flexible arc is deformed, strain is distributed substantially uniformly along the flexible arc;
Stent.
(35) In the stent according to embodiment 34,
Multiple flex connectors,
Have
Each of the bent connectors is formed so as to be nested in the bent connector adjacent in the circumferential direction.
Stent.

1 is a perspective view of an intraluminal stent in an unexpanded, ie, pre-constrained state, according to one embodiment of the present invention. 1 is a perspective view of an intraluminal stent in a fully expanded state, according to one embodiment of the present invention. FIG. 1 is a front view illustrating a stent in a state before being restrained and placed according to an embodiment of the present invention, and shows a state in which the stent is cut in a length direction and placed flat in a two-dimensional shape. Show. FIG. 4 is an enlarged detail view of a proximal hoop element, according to one embodiment of the present invention. FIG. 3 is an enlarged detail view of an internal hoop element according to an embodiment of the present invention. FIG. 4 is an enlarged detail view of a distal hoop element, according to one embodiment of the present invention. FIG. 4 is an enlarged detail view of a flex connector according to an embodiment of the present invention. FIG. 3 is an enlarged detail view of a tapered radial arc according to one embodiment of the present invention. It is a graph showing the length of the discontinuity taken on the X-axis with respect to the stress intensity range taken on the Y-axis (difference in stress intensity factor over the entire fatigue load). FIG. 6 is a graph depicting the fatigue life of a stent (taken on the Y axis) as a function of the magnitude of the discontinuity (taken on the X axis). 1 is an enlarged detail view of a stent section typically found in the prior art. FIG. FIG. 3 is an enlarged detail view of a stent section according to an embodiment of the present invention. FIG. 6 is a graphical representation of the strain that a stent section undergoes at various locations along the stent section.

Claims (27)

In the stent,
One or more hoops having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end Sections, each hoop section being formed as a series of radial strut members that are substantially longitudinally oriented and a plurality of radial arc members connecting adjacent radial strut members Being a hoop section,
With
At least one of the radial arc members such that strain and / or stress is distributed substantially uniformly along the at least one of the radial arc members when the at least one of the radial arc members is deformed; Has a non-uniform cross-section,
Stent. The stent of claim 1,
The stent wherein the at least one cross-section and the other cross- section of the radial arc member have cross-sectional areas that are substantially equal to each other . The stent of claim 1,
The stent wherein the at least one cross-section and the other cross- section of the radial arc member have cross-sectional areas that are not substantially equal to each other . In the stent,
One or more flex connectors having at least one flex component;
With
At least one of the bending components such that strain and / or stress is distributed substantially uniformly along the at least one of the bending components when the at least one of the bending components is deformed; Has a non-uniform cross-section,
Stent. The stent according to claim 4,
A stent wherein the bending component is a flexible arc member. The stent according to claim 5,
It said flexible section and with the arc member with another cross section, has a substantially equal cross-sectional area to each other, the stent. The stent according to claim 5,
Said flexible section and with the arc member with another cross section, has a cross-sectional area not equal to each other, the stent. The stent according to claim 4,
A stent wherein the bending component is a flexible strut member. The stent according to claim 8,
A stent wherein one cross-section of the flexible strut member and another cross-section have cross-sectional areas that are substantially equal to each other . The stent according to claim 8,
The cross section and with a flexible strut members and another cross-section, has a cross-sectional area not equal to each other, the stent. In the stent,
One or more radial support members having at least one radial component;
With
At least one of the radial components such that strain and / or stress is distributed substantially uniformly along the at least one of the radial components when the at least one of the radial components is deformed; Has a non-uniform cross-section,
Stent. The stent of claim 11,
A stent wherein the at least one of the radial components is a radial arc member. The stent of claim 12,
The radial arc member a sectional and a different cross-section, have substantially equal cross-sectional area to each other, the stent. The stent of claim 12,
The radial arc member a sectional and a different cross-section, has a cross-sectional area not equal to each other, the stent. The stent of claim 11,
A stent wherein the at least one of the radial components is a radial strut member. The stent of claim 15,
A stent wherein a cross-section of the radial strut member and another cross-section have cross-sectional areas that are substantially equal to each other . The stent of claim 15,
Wherein the cross-section and another section with a radial strut member has a cross-sectional area not equal to each other, the stent. In the stent,
Multiple hoop sections,
Each of the hoop sections has a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end. And
Each of the hoop sections includes a series of radial strut members that are substantially longitudinally oriented, and a plurality of radial arc members connecting adjacent radial strut members;
At least one of the radial arc members such that strain and / or stress is distributed substantially uniformly along the at least one of the radial arc members when the at least one of the radial arc members is deformed; A hoop section having a non-uniform cross-section;
One or more bending connectors oriented in a longitudinal direction connecting adjacent hoop sections, each bending connector comprising a flexible strut, each flexible strut being one possible A flex connector connected at each end by a flexible arc;
A stent. The stent according to claim 18,
Each said radial arc member is connected to two adjacent radial strut members respectively at first and second radial strut connection points;
At least one of the bent connectors is connected to the radial arc member of the end hoop section at a bent connector connection point located in the immediate vicinity of the first radial strut connection point of the radial arc member;
The radial arc member of the end hoop section, wherein the first radial strut connection point has an asymmetric geometric shape with a different cross section than the second radial strut connection point. The stent according to claim 18,
A stent wherein the radial strut members in at least one of the hoop sections are of equal length to each other. The stent according to claim 18,
A stent in which the flexible struts and the flexible arc that make up the flex connector are arranged in a substantially "N" shape. In the stent,
One or more hoops having a tubular shape having a proximal open end and a distal open end and defining a longitudinal axis extending between the proximal open end and the distal open end Sections, each hoop section being formed as a series of radial strut members that are substantially longitudinally oriented and a plurality of radial arc members connecting adjacent radial strut members Being a hoop section,
With
At least one of the radial arc members such that strain and / or stress is distributed substantially uniformly along the at least one of the radial arc members when the at least one of the radial arc members is deformed; Has a non-uniform outer shape,
Stent. The stent according to claim 22,
A stent wherein at least one of the radial strut members has a portion that is shaped to have a larger cross section. The stent of claim 23.
A stent wherein the portion is a ledge. The stent according to claim 22,
The one or more hoop sections include an inner hoop section and an end hoop section;
The stent wherein the axial length of the inner hoop section is longer than the axial length of the end hoop section. The stent according to claim 22,
The one or more hoop sections include an inner hoop section and an end hoop section;
The stent wherein the axial length of the inner hoop section is shorter than the axial length of the end hoop section. The stent according to any one of claims 18 to 21,
The one or more flex connectors include a plurality of flex connectors;
The stent, wherein each of the bent connectors is formed so as to be nested in the bent connector adjacent in the circumferential direction.

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